QUASI-PARTICLES IN THE VORTEX STATE OF V3SI

Low-energy quasiparticle excitations in the vortex state of the superc onductor V3Si have been investigated using the de Haas-van Alphen effe ct. Quantum oscillations persist to surprisingly low values of B0/B(c2 ) is similar to 0.6 and T/T(c) is similar to 0.001. The superconductin g state introduces a field-dependent quasiparticle damping which has a value HBAR tau-1 almost-equal-to 0.25 DELTA at the lowest fields inve stigated, considerably less than the superconducting gap DELTA. Quantu m oscillations are attributed to the presence of a gapless excitation spectrum and may be a universal characteristic of superconductors in t he vortex state.